The existing communication networks such as a Packet Transport Network (PTN) can be divided into frequency synchronous networks and time synchronous networks. Herein, the frequency synchronous networks use a Synchronous Ethernet (SyncE) or a Precision Time Protocol (PTP) to extract clock information from a physical code stream or a packet message, and adopt a Synchronization Status Message (SSM) for frequency source selection and path switching; while the time synchronous networks use the PTP to extract timestamp information from a timing message, calculate a time deviation and perform time calibration. The time synchronous networks use the PTP for time source selection and path switching. There are several thousand devices in the PTN, which leads to a heavy workload to maintain the network. Each device in the PTN can be used as a Network Node (NE), and once a reference source and/or a synchronization link in the PTN fails, as the existing PTN lacks an effective switching mechanism when the failure occurs, it cannot guarantee the real-time performance of switching of the synchronization link.